As an air-conditioning apparatus, there is an apparatus in which a heat source unit (outdoor unit) is disposed outside a building and an indoor unit is disposed inside the building, for example, as in a multi-air-conditioning apparatus for building. A refrigerant circulating through a refrigerant circuit of such an air-conditioning apparatus rejects heat to (or removes heat from) air supplied to a heat exchanger of the indoor unit, thereby heating or cooling the air. Then, the heated or cooled air is sent to an air-conditioned space, thereby performing heating or cooling.
A building generally includes a plurality of indoor spaces, and thus such an air-conditioning apparatus also includes a plurality of indoor units accordingly. In addition, in the case where the size of the building is large, a refrigerant pipe connecting the outdoor unit to the indoor unit may be 100 m. When the length of the pipe connecting the outdoor unit to the indoor unit is long, an amount of the refrigerant injected to the refrigerant circuit is increased due to the long pipe.
Each indoor unit of such a multi-air-conditioning apparatus for building is generally disposed and used in an indoor space where a person is present (e.g., an office space, a living room, a store, etc.). When the refrigerant leaks from an indoor unit disposed in an indoor space for a certain reason, there is a possibility that the leak becomes problematic in terms of effect on human body and safety, since the refrigerant is flammable or toxic depending on its type. In addition, even when the refrigerant is not harmful to human body, it is also assumed that the oxygen concentration in the indoor space decreases due to the refrigerant leak, which influences on human body.
In order to deal with such a problem, a method is conceivable in which a two-loop system is employed in an air-conditioning apparatus, a refrigerant is used in a primary loop, harmless water or brine is used in a secondary loop to perform air-conditioning on a space where a person is present, the refrigerant in the primary side is used to perform direct air-conditioning on a shared space such as a corridor (e.g., see Patent Literature 1).
However, in the above system in which both air-conditioning with the refrigerant and air-conditioning with water or brine are performed, it is impossible to clearly determine which spaces air-conditioning with the refrigerant and air-conditioning with water or brine are selectively used.